The present invention relates to an automatic leveling device for automotive vehicle headlamps for controlling the driving of optical axis tilt adjusting actuators based on an inclination in a longitudinal direction of a vehicle (hereinafter, referred to as a pitch angle). A pitch angle detection means detects and automatically tilt adjusts the optical axes of the headlamps (hereinafter, referred to as automatic leveling) in a direction to offset an angle corresponding to the detected pitch angle. In addition, the automatic leveling device includes a fail safe function that automatically stops driving the optical axis tilt adjusting actuators should they happen to fail.
Known automatically adjustable headlamps include a reflector having a light source securely inserted therein and supported in such a manner as to be tilted around a horizontal tilt shaft relative to a lamp body. The optical axis of the reflector (headlamp) is tiltable around the horizontal tilt shaft by means of an actuator. A conventional automatic leveling device includes a pitch angle detection means, a vehicle speed sensor, a controlling section for controlling the driving of an actuator based on signals from the detection means and sensor, and the like, all of which are mounted on a vehicle. The optical axes of the headlamps (reflectors) are adjusted so as to stay in a certain state with respect to the surface of the road at all times.
In the conventional automatic leveling device, however, no countermeasures are provided against a failure of the actuators. Thus, if the actuators fail and become inoperable, the optical axes of the headlamp are fixed in the position where they were directed when the actuators failed. If the optical axes are fixed as being directed more upwardly than a desirable level, although the driver of the subject vehicle can get good visibility, a driver of an oncoming vehicle will be dazzled by the light from the headlamps. Conversely, if the optical axes are fixed as being directed too low, although there is no problem for oncoming vehicles, the visible distance is shorter and may cause the driver to detect an object on the road too late, thus putting the driver into a dangerous situation.